This invention pertains to a knee action circuit connector attached to an internal magnetic shield within a cathode-ray tube.
A color cathode-ray tube (CRT) typically has an internal magnetic shield (IMS) to reduce the influence of magnetic fields on electron beam trajectories as a cathodoluminescent screen of the tube is scanned. The IMS is usually made of 0.1 mm thick cold-rolled steel and is fastened to a shadow-mask support frame so that the IMS and frame are magnetically coupled. The IMS is designed to fit into the funnel and be as close to the funnel wall as possible, but should not touch the funnel to avoid any friction between the IMS and a conductive anode coating on the inner surface of the glass funnel.
It has been conventional practice to attach a flexible contact spring to the rear portion of the IMS for effecting an electrical connection between the shield and the conductive coating on the inner surface of the funnel. One example of such a contact spring is shown in U.S. Pat. No. 4,670,686. This patent shows a contact spring attached to a rear portion of the IMS and extending forward toward the screen to a free end which contacts a conductive anode coating on the inner surface of the glass funnel. The IMS and contact spring assembly are loaded into the funnel from the front before application of the faceplate panel over a frit seal surface located at the front of the funnel As the IMS and contact spring assembly are loaded, the contact spring tends to engage the frit seal surface of the funnel and drag across both the frit seal surface and the conductive anode coating inside the funnel. This can cause frit particles to be introduced into the CRT as a contaminant which may later block apertures in the shadow mask through which electron beams pass from the electron gun to the screen or cause other detrimental effects.
The invention provides a cathode-ray tube (CRT) having a funnel sealed at one end to a faceplate panel with a viewing screen on an interior surface thereof wherein the funnel includes an internal conductive coating electrically connected to an anode button on the funnel. A mask frame support assembly is secured in proximity to the screen and includes an internal magnetic shield having an exterior surface extending along at least a portion of the inside surface of the funnel. A knee action circuit connector is disposed between the exterior surface of the magnetic shield and the inside surface of the funnel and extends from the magnetic shield to form a curved first contact portion resiliently engaging the conductive coating of the funnel and a second contact portion extending from the curved portion and urged inwardly against the exterior surface of the internal magnetic shield thereby making electrical contact between the conductive coating and the internal magnetic shield to complete an electrical circuit between the anode button and the IMS.